Washing agents and process for machine washing of dishes



Jan. 14, 1969 ET AL 3,421,940

WASHING AGENTS AND PROCESS FOR MACHINE WASHING OF DISHES Filed Jan. 15, 1962 INVENTORS HANS WEDELL ROLF PEIST BYHMWLAQ-ZML ATTORNEYS United States Patent 3,421,940 WASHING AGENTS AND PROCESS FOR MACHINE WASHING 0F DISHES Hans Wedeil and Rolf Peist, Dusseldorf-Holthausen, Germany, assignors to Bohme Fettchemie G.m.b.I-I., Dusseldorf, Germany, a corporation of Germany Filed Jan. 15, 1962, Ser. No. 166,072 Claims priority, application Germany, Jan. 27, 1961, B 61,028; Mar. 23, 1961, B 44,623 US. Cl. 13429 4 Claims Int. Cl. B08b 3/02; A471 15/00; Clld 1/82 ABSTRACT OF THE DISCLOSURE Improvement of a machine dishwashing process which is widely used in practice and in which an alkaline principal washing cycle and a neutral rinsing cycle with surfactive substances are employed and the spent rinsing water is continuously or discontinuously sent into the principal washing cycle. The well known process has been improved by the present invention in that solid, silicon-containing agents in chunk or powder form are used for the principal washing cycle.

PRIOR ART The machine washing of dishes usually consists of a three-step process in which the dishes are first treated with a soluiton of an alkaline washing agent, then the dishes are rinsed with a solution of a neutral non-ionic rinsing agent, and finally the dishes are dried to obtain film-free dishes. The washing and rinsing solutions are usually pumped through nozzles or propellers to wash the dishes which are held in racks. The alkaline washing agent removes and disperses the food scraps from the dishes while the neutral non-ionic rinsing agent is used to provide filmfree drainage of the alkaline washing solution from the dishes so that after drying no residues remain and the dishes appear shiny and clear.

The alkaline washing solution in the first stage is usually recycled. Because the solution becomes highly contaminated with foreign matter during continuous reuse, part of the contaminated solution is purged continuously or intermittently by overflow and is replenished by fresh solution, usually by the addition of spent, hot rinsing solution. The rinsing solution is replenished by a fresh solution of rinsing agent.

The washing and rinsing agents should be substantially non-foaming since foaming reduces the mechanical effectiveness of the sprayed solution and is thereby detrimental to the cleaning effect. Also, a high degree of foaming displaces some of the washing solution from the machine so that the washing cycle is unfavorably influenced. The alkaline washing agents have, as a rule, very low foaming properties while the non-ionic rinsing agents tend to have a higher degree of foaming properties. The foaming action of the non-ionic rinsing agents can be reduced by the addition of fatty acids or soaps or by selection of specific mixtures of polyglycol ethers of high molecular weight aliphatic alcohols or phenols or by concurrent use of polypropylene addition products. However, even these rinsing solutions foam considerably in the presence of alkaline agents and fatty and protein-containing food scraps. Also, if certain minimum temperatures are not used, there will be a strong increase in the foaming action of the rinsing agent. Therefore, the recycling of the non-ionic rinsing solution to replace the alkaline washing solution purged has led to intolerably high foaming in the first washing stage which reduces the washing effect considerably.

3,421,940 Patented Jan. 14, 1969 OBJECTS OF THE INVENTION It is an object of the invention to provide improved alkaline washing agents for use in recycling dishwashers which will not foam.

It is another object of the invention to provide an improved process for the washing of dishes without foaming action.

These and other objects and advantages of the invention will become obvious from the following detailed description.

THE INVENTION Referring to the drawing, the figure illustrates one type of automatic dosing device which may be used to add the alkaline washing agent to the solutions.

The improved compositions of the invention are alkaline washing agents to which has been added 0.5 to 2.0 percent, preferably 0.2 to 0.5 percent, by weight of a silicone. The alkaline washing agents are well known mixtures of inorganic salts such as alkali metal salts of phosphates, silicates, carbonates, and hydroxides, and are used in concentrations of about 0.5 to 5 grams per liter of washing solution. They may be in the form of solids, lumps, or powders.

The silicones which are added to the alkaline washing agents are polymeric organosiloxanes wherein the silicon atoms are substituted with lower alkyl radicals such as methyl or ethyl radicals or aryl radicals such as phenyl radicals or combinations thereof such as methyl and phenyl radicals, preferably methyl groups. The said compounds are readily available commercially, available under the name silicones either as the compounds alone or in the form of solutions or emulsions.

It is already known to use silicones as additives for preparing aqueous soap solutions, but it could not be expected that silicones would be effective in very alkaline rinsing solutions, because normally they are disintegrated by alkali. (See: Silicones and Their Uses by Rob Roy McGregor, McGraw-Hill Book Co., New York (1954), page 260; Chemie und Technologie der Silikone by Prof. Dr. Walter Noll, publication Chemie G.m.b.H., Weinheim/Bergstr. (1960), page 296; H. Reuther, S. Sliwinski:

Uber Silikone XVII Schaumbekampfung durch den Einsatz von Silikonen, Chem. Techn., 5th annual set (June 1953), number 6, pages 306 and 307.)

If desired, other anti-foaming agents such as soaps, propylene oxide-ethylene oxide adducts, condensation products of ethylene oxides, and high-molecular weight fatty alcohols with blocked terminal hydroxyl groups or fatty alcohols with 6 to 12 carbon atoms may be added to the alkaline washing agent to enhance the activity of the silicones.

The novel process of the invention for machine washing of dishes comp-rises spraying the dishes with a hot solution of an alkaline washing agent containing 0.05 to 2 percent of a silicone to clean the dishes, purging part of washing solution to remove contaminating food particles, recycling the washing soution, rinsing the dishes with a solution containing about 0.1 to 1 gm. Per liter of a neutral non-ionic washing agent to permit film-free drainage of the dishes, dissolving the alkaline washing agent in the spent rinsing solution, mixing the resulting solution with the recycled solution of the alkaline washing agent and dnyi'ng the dishes. If necessary, hot or cold fresh water may be added to the spent rinsing agent to control the pH of the alkaline washing solution.

The alkaline washing agent containing silicones may be added to the spent rinsing solution by hand but is preferably added by passing the spent rinsing solution through a dosing container containing the alkaline washing agent as illustrated in the figure.

The dosing apparatus consist of a cylindrical or rectangular conatiner 1 which is closed by means of a cover 2. The cover 2 may be immovably connected with the container 1 by means of a thread or other fastening means. The combined intake and discharge system 3 is mounted on cover 2 by means of a screw thread 4 or similar means. The combined system 3 consists of an intake stud 5 provided with a control screw 6 for the spent rinsing solution, a tube 7 and a discharge fitting 8 for the resulting alkaline washing solution. The tube 7 is provided with a screen 9 at its lower discharge opening. The alkaline washing agent containing silicones may be filled either directly into container 1 or into an insert container 10 sealed against the cover and the Walls of container 1 by means of a washer 11. The washer 11 may, for example, be constructed by means of a solid connection with the insert container so that the operation of the device is not possible without this container. The insert container may consists of a plastic foil and may serve as the shipping container and sales package for the alkaline washing agent containing silicones.

In operation of the device the alkaline washing agent is introduced into container 1 and the container is tightly closed with the aid of cover 2 which has the intake and discharge system 3 mounted thereon. During operation of the apparatus the spent rinsing solution enters through the intake fitting 5, passes the control screw 6, and comes in contact with the substance in the container through intake tube 7. The finished solution is carried to the place of employment through the discharge fitting 8.

The rate of dissolution of the alkaline washing agent and the concentration of the solution is controlled in this device through the solvent temperature, the amount of solvent used per unit of time, and the amount of solid substance employed. For this reason the apparatus can be provided with containers 1 of various sizes. With the aid of containers of different sizes, the concentration can not only be regulated by means of the solvent intake rate but also by means of different amounts of substance to be dissolved.

By using the process of the invention, the selection of the rinsing agent is not limited to the small class of lowfoaming non-ionic products or soap-containing mixtures of non-ionic products and compounds which have better wetting properties may now be used as rinsing agents. Prior to applicants invention these compounds could not be used due to their strong foaming properties.

While surfactive compounds or mixture of said compounds such as alkyl sulfates, alkyl sulfonates, and alkylbenzene sulfonates are suitable rinsing agents, it is preferred to use as rinsing agents non-ionic compounds such as the condensation products of ethylene oxide or ethylene oxypropylene oxide with high-molecular weight lipophilic compounds which have exchangeable hydrogen atoms attached to the molecule through oxygen, sulfur or nitrogen atoms and ethylene oxide-propylene oxide condensation products which are sold under the trade name of Pluronics.

In the following examples there are described several preferred embodiments to illustrate the invention. However, it should be understood that the invention is not intended to be limited to the specific embodiments.

Example I A powdery alkaline salt mixture having the following composition:

was continuously added in measured amounts by means of the dosing device illustrated in the figure to the main washing solution of a dishwashing machine. The addition was accomplished so that the washing solution had a constant concentration of 2 gm./liter of the alkaline salt mixture dissolved therein. The working temperature of the washing solution was 50 C. As a rinsing agent the addition product of 6 mols of ethylene oxide to 1 mol of nonylphenol was used in the rinsing solution in a concentration of 0.5 gm./liter. The spent solution Was in part used to dissolve the above salt mixture and was continuously fed into the main washing solution tank.

Even after several hours of operation the alkaline washing solution exhibited no foam formation. The dishes left the washing machine after the drying cycle in clean and film-free condition. When an analogously composed washing agent without the silicone additive was used, the foaming properties of the washing solution increased within a few minutes to such an extent that the alkaline washing solution no longer possessed the necessary mechanical energy for cleansing the dishes.

Example 11 Washing agent tablets having the following composition:

Parts by weight Soda 20 Chlorine-containing trisodium phosphate 3O Hexametaphosphate 20 Sodium salt of ethylenediamine tetraacetic acid 10 Sodium silicate 19.95

Silicone oil (anti-foaming agent SH by Wacker Chemie G.m.b.H.) 0.05

were intermittently added to the main washing solution of a dishwashing machine by means of a dosing device which was controlled by the pH-value of the washing solution. The addition of the tablets was controlled so that the Washing solution had a constant pH-value of 9.5. The working temperature of the Washing solution was 70 C. The rinsing agent was the addition product of 12 mols of ethylene oxide and 9 mols of propylene oxide to 1 mol of octylphenol and was present in the rinsing solution at a concentration of 0.1 gm./liter. The spent rinsing solution flowed into the main washing solution and thereby freshened the latter.

Even during continuous operation the washing solution exhibited no foaming of any kind. When a washing agent having an analogous composition but without the silicone additive was used, the foaming properties of the washing solution increased to an intolerable degree.

Example III At intervals of 15 minutes, 50 gm. of a powdery washing agent having the following composition:

Percent Tripolyphosphate 50 Trisodiumphosphate 20 Sodium silicate 28 Silicone oil (methylpolysiloxane, relative viscosity about 500) 2 was added by hand to a washing solution of a continuous ly operating dishwashing machine. The addition of the powdery washing agent was controlled so that, taking into consideration the amount of rinsing solution being added thereto, the washing solution constantly contained 1 gm./ liter of the salt mixture in solution. The rinsing agent was an aqueous solution containing 20% of the addition product of 9 mols of ethylene oxide to 1 mol of dodecylphenol and 4% of the addition product of ethylene oxide to polypropylene glycol ether, which is commercially available under the mark Pluronic L 61. This rinsing agent was automatically added so that the rinsing solution contained 1 gm./liter thereof in solution.

Even after several hours of operation the alkaline washing agent solution exhibited no foam formation of any kind. However, when a washing agent of analogous composition but without the silicone additive was used, the foaming properties of the washing solution increased so much within a short period of time that satisfactory cleansing of the dishes was no longer possible.

Various modifications, of the process and compositions of the invention may be made without departing from the spirit or scope thereof, and it is to be understood that the invention is to be limited only as defined in the appended claims.

We claim:

1. A process for washing dishes consisting essentially of spraying the dishes with a hot aqueous solution of an inorganic alkaline washing agent containing 0.05 to 2 percent of a polymeric organosiloxane wherein the silicon atoms are substituted with at least one member of the group consisting of lower alkyl and aryl radicals to clean the dishes, purging part of the said washing solution to remove contaminating food particles, recycling the said washing solution, rinsing the dishes with a solution containing about 0.1 to 1 gram per liter of a neutral nonionic rinsing agent to permit film-free drain-age of the dishes, dissolving inorganic alkaline washing agent containing said polymeric organosiloxane in the spent rinsing solution, mixing the resulting solution with the recycled solution of the solid, inorganic alkaline washing agent, and drying the dishes.

2. The process of claim 1, wherein the alkaline washing agent contains 0.2 to 0.5 percent of a polymeric organosiloxane.

3. The process of claim 1, wherein the polymeric organosiloxane is methylpolysiloxane.

4. A continuous process for the washing of dishes consisting essentially of moving the dishes continuously through a washing zone wherein the dishes are sprayed with a hot, aqueous solution of an inorganic alkaline washing agent containing 0.05 to 2 percent of a polymeric organosiloxane wherein the silicon atoms are substituted with at least one member of the group consisting of lower alkyl and aryl radicals to clean the dishes, and part of the washing solution is purged to remove contaminating food particles and the remainder of the washing solution is recycled, a rinsing zone wherein the dishes are rinsed with a solution containing about 01 to 1 gram per liter .of' a neutral rinsing agent to permit film-free drainage of the dishes, and the spent rinsing solution is used to dissolve the solid, inorganic alkaline washing agent containing said polymeric organosiloxane and is added to the recycled solution of the inorganic alkaline washing agent and a drying zone wherein the dishes are dried.

References Cited UNITED STATES PATENTS 2,359,913 10/1944 Hill 134-34 XR 2,509,003 5/1950 Lathrop et al. 134-29 XR 2,677,630 5/1954 Scales 134-29 XR 2,739,903 5/1956 Arnold 134-29 XR 2,829,112 4/1958 Solomon 252-358 2,894,913 7/1959 Sullivan et al. 252-358 2,930,721 3/1960 Tuthill 134-26 XR 2,982,723 5/1961 Arnold et al. 134-29 MORRIS O. WOLK, Primary Examiner.

I. ZATARGA, Assistant Examiner.

US. Cl. X.R. 134-10, 25, 36 

